Analysis for determining surface free energy uncertainty by the Owen–Wendt method

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Metalworking fluids—Mechanisms and performance

This work shows the influence of solid–liquid interactions between engineering surfaces (steel and several types of DLC coatings) and lubricating oil (polyalphaolefin, PAO) on the coefficient of friction in the elastohydrodynamic lubrication (EHL) regime. Specifically, it confirms that the spreading parameter, rather than the contact angle, is the relevant parameter to evaluate the wetting behaviour of these surfaces with oils. Both the spreading parameter and the surface energy correlate very well with the friction in the EHL regime and can predict its behaviour. In particular, the polar component of the surface energy was found to correlate almost perfectly with the friction behaviour (a Pearson’s linear correlation coefficient of 0.999). By tailoring the wetting and surface energy—achieved by varying the DLC/DLC contacts with different types of DLC coatings—the coefficient of friction in the EHL regime was reduced by more than 30 % compared to steel/steel contacts. Poor wetting of the DLC coatings with a low surface energy is reflected in low values of the spreading parameter, which indicates easier slip of the lubricant over the solid surface due to shear action, and this leads to a lower viscous friction. A “Slip-inducing interaction model based on surface forces” is presented to explain why oil slip is promoted, particularly at surfaces with a low polar surface energy. The model suggests that a small number of permanent polar interactions, i.e. a larger proportion of intermittent dispersive interactions, results in less adhesive interactions between the predominantly non-polar liquid (oil) and the low polar surface (DLC), which enables easier slip at the solid–liquid interface.

The Effect of Wetting and Surface Energy on the Friction and Slip in Oil-Lubricated Contacts

An in situ characterization method for mechanical and adhesive properties of organic/ceramic composite membranes is built on the basis of nanoindentation technique in this work. The polydimethylsiloxane (PDMS) was used as the separation layer with the support of porous ZrO2/Al2O3 ceramic tubes. The effects of roughness of the ceramic support and the viscosity of PDMS solution on the mechanical properties of the PDMS separation layer and the interfacial adhesion at the interface were investigated in detail. It was found that when the roughness of the ceramic support increased and the viscosity of PDMS solution decreased, the interfacial adhesion strength of PDMS/ceramic composite membrane increased, but these two variables had little effect on the mechanical properties of the PDMS separation layer. Our results indicate that the mechanical interlocking dominates the adhesion between the PDMS separation layer and the porous ceramic support. V C 2009 American Institute of Chemical Engineers AIChE J, 56: 1584–1592, 2010

Interfacial adhesion between polymer separation layer and ceramic support for composite membrane

Proper coating selection for improved galling performance of forming tool steel

Surface free energy is a characteristic factor which affects the surface properties and interfacial interactions such as adsorption, wetting and adhesion. Surface free energy is thus of interest in the field of adhesive technologies, biomedical applications, cleaning procedures or for the wettability of tribological systems. One method of determining the polar and dispersive terms of the free surface energies of solids is based on measurements of the contact angles of pure liquids on solid surfaces. This paper describes the use of dynamic contact angle analysis for the evaluation of surface tension.

E Lugscheider

Papers

The influence on surface free energy of PVD-coatings